rc is a command interpreter and programming language similar to
sh(1). It is based on the AT&T Plan 9 shell of the same name.

The shell offers a C-like syntax (much more so than the C shell),
and a powerful mechanism for manipulating variables. It is reasonably
small and reasonably fast, especially when compared to contemporary
shells.  Its use is intended to be interactive, but the language
lends itself well to scripts.
